1. Field of the Invention
The present invention relates to an illumination apparatus and an exposure apparatus used in semiconductor manufacturing, and, more particularly, to compensation of angular and positional deviations of a laser beam in the exposure apparatus having an excimer laser source.
2. Discussion of the Related Art
In an illumination apparatus according to the specification and drawings of Japanese Patent Utility Model H7-120862 (filed Apr. 21, 1995), a first four-point-probe four-directional sensor detects angular deviation of a laser beam relative to a design optical axis, and a second four-point-probe sensor detects positional deviations of the laser beam relative to the design optical axis. The measurement performed by such a four-point-probe sensor generally is inaccurate. In this example of conventional technology, errors in measurement often occur when an intensity distribution of the laser beam varies. Additionally, the first detecting system for angular deviation of the laser beam and the second detecting system for positional deviation of the laser beam must be independently located and the overall size of the apparatus tends to be large.